Cardiovascular disease is the leading cause of death worldwide. Although drug treatment of cardiovascular disease is increasing, two of the primary methodologies currently used to treat cardiovascular disease are coronary artery bypass grafts and percutaneous coronary intervention, commonly referred to as angioplasty.
During an angioplasty procedure, a stent is often implanted into a restricted blood vessel to open the diameter of the blood vessel. Various types of stents are currently known for such procedures. Each type of stent has certain advantages, but each type also suffers from one of several known complications or weaknesses, including: restenosis, the need for long term use of anticoagulants, inhibition of natural blood vessel motion (such as pulsatile motion), in-stent thrombosis, improper healing, and potential for fracture of the stent.
In contrast to percutaneous coronary intervention, a coronary artery bypass graft implants a graft to bypass a blockage or obstruction in a coronary artery. Various types of grafts have been used for bypass surgeries, including biological grafts (e.g. autografts, allografts and xenografts) as well as artificial grafts (e.g. ePTFE, PTFE and PET). Additionally, although not widely used, tissue-engineered grafts are being developed in which the graft is produced in vitro.
Although each of the known grafts has certain advantages, such as cost, availability or similarity to native tissue, each of the known grafts also suffers from one of several known complications or weakness. For instance, autografts typically have shorter durability and higher incidences of failure rate compared with artificial grafts, while allografts typically require long term use of anti-rejection medication. Artificial grafts are readily available, but may be more prone to infection, thrombosis or intimal hyperplasia and may require long term use of medication, such as anticoagulants. Although tissue-engineered grafts overcome many of the problems associated with commonly-used biological and artificial grafts, tissue-engineered grafts are extremely expensive and take a long time to manufacture.
In general, native vessels remain the preferred choice for revascularization procedures, however, such tissues are not always available. In such cases, synthetic materials such as expanded polytetrafluoroethylene and polyethylene terephthalate have been used successfully as vascular conduits when the graft diameter exceeds 6 mm. Results have been poor, however, with grafts less than 6 mm in diameter, due to the development of thrombi and intimal hyperplasia.
These and other drawbacks are associated with current implantable lumens and methods used for forming implantable lumens.